What is Genetic Engineering?
What is Genetic Engineering?
Genetic engineering is like cut and paste for genes. Find a useful gene in one organism (e.g., human insulin gene), CUT it out with enzyme "scissors," then PASTE it into another organism (e.g., bacteria). Now the bacteria produces human insulin!
Directly modifying an organism's DNA to give it new characteristics:
- Identify the gene for desired characteristic
- Cut out the gene using enzymes
- Insert gene into vector (e.g., plasmid, virus)
- Transfer vector into target organism
- Gene is expressed — organism shows new characteristic
Biology glossary
- What is genetic engineering?
- The direct modification of an organism's genome by inserting a gene from another organism (or a modified gene) to give it a new or altered characteristic. The resulting organism is called a genetically modified (GM) organism.
Genetic engineering is like cut and paste for genes. Find a useful gene in one organism (e.g., human insulin gene), CUT it out with enzyme "scissors," then PASTE it into another organism (e.g., bacteria). Now the bacteria produces human insulin!
Earn the mark scheme marks
Memory Aids
CLIP — the four steps of inserting a gene:
"You CLIP the gene in."
- C — Cut with restriction enzyme (scissors)
- L — Ligase seals the gene into the vector
- I — Insert recombinant vector into host organism
- P — Produce the desired protein
Enzyme roles:
- Restriction enzyme = scissors (cuts)
- Ligase = glue (joins)
- "Restriction scissors, Ligase glue — CLIP the gene through."
Insulin example — a model answer anchor:
Human insulin gene → restriction enzyme cuts it out → ligase inserts it into bacterial plasmid → bacteria take up plasmid → bacteria cultured in fermenter → insulin harvested and purified → given to diabetic patients.
Quick Check: Describe the role of each of the following in the production of human insulin using bacteria: (a) restriction enzyme, (b) ligase, (c) plasmid.
(a) Restriction enzyme: cuts the human insulin gene out of the human chromosome at specific restriction sites, and also cuts the bacterial plasmid open. Both cuts leave complementary sticky ends. (b) Ligase: joins (ligates) the sticky ends of the insulin gene to the sticky ends of the open plasmid, permanently sealing the gene into the plasmid and forming the recombinant plasmid. (c) Plasmid: acts as the vector — the circular ring of DNA that carries the insulin gene into the bacterial host cell. When bacteria reproduce, the plasmid is copied and passed to daughter cells, so all daughter cells also contain and express the insulin gene.
Quick Check: Evaluate the use of genetically modified (GM) crops that are resistant to insect pests. Include both advantages and disadvantages in your answer.
Advantages: Fewer crops are destroyed by pests, increasing yield and food security. Less chemical pesticide is needed, reducing environmental pollution and costs for farmers. Plants grow more vigorously without insect damage. Disadvantages: Modified genes could spread to wild plant relatives through pollen, potentially creating herbicide- or insect-resistant weeds ("superweeds"). Insects that are not pests might be harmed by the toxin produced. Long-term ecological effects are not fully known. There are ethical concerns about corporate control of food supply (large companies own GM seed patents). Public acceptance is low in some countries. The scientific consensus is that approved GM crops are safe to eat, but environmental impacts remain debated.
Quick Check: Explain why the same restriction enzyme must be used to cut both the donor gene and the vector plasmid in genetic engineering.
Restriction enzymes cut at specific recognition sequences, leaving sticky ends — short, single-stranded overhangs with unpaired bases. For the gene to join to the plasmid, the sticky ends of the gene must be complementary to the sticky ends of the plasmid. This complementarity is only guaranteed if both were cut by the same restriction enzyme, because the same enzyme always produces the same sticky end sequence. If different enzymes were used, the sticky ends would have different sequences and would not be complementary, so base pairing could not occur and ligase could not join them together.
Now try it yourself
Quiz · Question 1 of 24
Which of the following is a benefit of genetic engineering?
Tap an answer to check it
This topic in real past papers
Every real exam question we've found on genetic engineering, with a full worked answer.